For anyone using the Nexus 1000V virtual switch, it’s sometimes useful to see what is happening directly on the Virtual Ethernet Module (VEM) residing on the host, rather than just having visibility from the Virtual Supervisor Module (VSM). The method to achieve this is via the ‘vemcmd’ syntax on the ESXi host. Unfortunately these commands are not well documented, so I thought it would be useful to provide a list of some of the more common ones.

When the Nexus 1000V was first released, the only available control mode between VSM (Virtual Supervisor Module) and VEM (Virtual Ethernet Module) was layer 2 mode. This meant that the VSM and VEM had to be layer 2 adjacent (i.e. on the same VLAN). Layer 3 control mode was released a while ago however, which meant that the VSM and VEM could be on different VLANs / subnets. L3 control also makes things slightly simpler to set up as you don’t need to worry about trunking control / packet VLANs everywhere and setting up port groups for these.